1. Field of the Invention
The present invention relates to two-cycle engine oil compositions and to ester base stocks which are components thereof. These two-cycle engine oil compositions require no miscibility-enhancing solvents and are readily biodegradable.
The present invention further relates to grease formulations and to ester base stocks which are components thereof. These grease formulations are largely biodegradable.
2. Description of the Related Art
Great efforts have been made in recent years to develop and employ more and more products and technologies that are compatible with the environment. This trend began with a search for biodegradable oils for outboard engines and biodegradable oils for chain saws. Likewise, there has been a search for a new generation of lubricating greases in agriculture, the central lubrication of truck chassis, in wastewater purification plants, in hydro-electric power plants and for the lubrication of rails, wheel flanges and switches on the railways.
The two-cycle (two stroke) engine has gained considerable popularity as a power source for such devices as outboard motors, snow mobiles, mopeds and a variety of landscaping equipment, e.g., lawnmowers, chain saws, string trimmers and blowers. The widespread use of two-cycle engines is due primarily to their simple design and lightweight construction, their ability to provide high power output with quick starts at low temperature and their relatively low cost.
Two-cycle engines are operated using a mixture of gasoline and a lubricant in prescribed proportions. The lubricant must provide satisfactory performance characteristics under severe operating conditions. Lubricants for two-cycle engines are generally composed of a mineral oil or synthetic base fluid, performance additive(s) and a solvent, ordinarily a relatively low boiling petroleum distillate, to enhance gasoline/lubricant miscibility.
The technologies developed to date for reducing exhaust emissions from four-cycle car and truck engines have not been successfully adapted to two-cycle engines. Hence, there is growing public concern over the high levels of hydrocarbon emissions from these small engines, as hydrocarbons do not readily biodegrade.
The hydrocarbon emissions are a consequence of the basic design of the engine. Specifically, in the power stroke of a typical two-cycle engine, air, oil and fuel are drawn into the crank case as the combined charge is compressed in the space above the piston. In the exhaust stroke, the burnt gases are discharged through exhaust ports, and a fresh combustible charge is transferred from the crank case to the space above the piston. Because the exhaust ports open before and close after transfer of the fresh combustible charge occurs, as much as 20% of the fresh charge will be discharged unburnt with the exhaust. Consequently, hydrocarbon emissions far exceed the level of emissions from a comparable four-cycle engine.
Water-cooled outboard motors exhaust directly into the water, giving rise to water pollution, whereas the other devices mentioned above, which are equipped with air-cooled two-cycle engines, produce emissions that pose a serious air pollution problem. For example, the California Air Research Board has determined that many two-cycle engines produce up to fifty times the pollution of truck engines per horsepower hour.
The above-noted pollution problems are exacerbated by the presence of volatile organic solvents in the lubricant. Moreover, some of the solvents used as miscibility enhancers, such as Stoddard solvent, have relatively low flash points, thus creating a potential fire risk, which is of particular concern in connection with the storage and transportation of such products.
Thus, a need exists for a two-cycle engine oil composition which is formulated so as to prevent pollution by protecting against emission of harmful hydrocarbons into the environment, and to reduce the hazard potential of the solvent-containing lubricants, especially in storage and in transit. These objectives must be obtained, however, while simultaneously satisfying stringent performance standards, e.g., good lubricity and detergency, particularly on piston rings, superior anti-seizure properties and high gel/floc resistance, and providing optimum miscibility of lubricant and fuel over the applicable range of operating conditions.
A grease may be made from oil that is thickened with a gelling agent, as for example, a soap. The common gelling agents (thickeners) used to make greases are the fatty-acid soaps of lithium, calcium, sodium, aluminum and barium, in concentrations of 3-25 wt %.
Chemical additives similar to those used in lubricating oils also may be added to grease to improve the properties of the grease as, for example, oxidation resistance, rust protection, and extreme-pressure (EP) properties.
Up until recently, very few synthetic oils have been used extensively in the formulation of lubricating greases. This reflects the ability of greases based on the natural oils derived from petroleum and its products to satisfy the market. Up until now, it has not been generally recognized that suitable greases can be made using certain biodegradable synthetic materials.
CEC-L-33-T-82 identifies a test method developed by the Coordinating European Council (CEC) and is reported by the CEC in xe2x80x9cBiodegradability of Two-Stroke Cycle Outboard Engine Oils in Water: Tentative Test Method,xe2x80x9d pp. 1-8, which is incorporated herein by reference. Using this test method, mineral oils are 15%-30% biodegradable, and natural vegetable oils are 70% to 95% biodegradable. Esters are up to 95% biodegradable, depending on chemical structure. Generally, a material that is classified by the CEC test as  greater than 70% is xe2x80x9crapidly biodegradablexe2x80x9d; see the paper of Dr. Dirk Loderer of Kluber Lubrication, Munich, Germany, presented at the National Lubricating Grease Institute in October, 1994. That terminology is adopted in describing the present invention. In addition, the term xe2x80x9creadily biodegradablexe2x80x9d is used to refer to a material that is xe2x89xa780% biodegradable.
The descriptions of grease formulations in the patent literature are generally silent with respect to biodegradability. The grease formulations made according to the examples that follow have been shown to be rapidly biodegradable. Typical of some of the prior art lubricating greases in the literature are those described in U.S. Pat. Nos. 3,622,512 and 4,879,054, described below, both of which patents are incorporated herein by reference.
The present invention provides a novel grease formulation that is based on the use of a base stock which is an ester of a C12-C20 monocarboxylic acid. The greases that comprise these specially selected polyol esters are not only reliable but are also rapidly biodegradable.
The base stock in the inventive grease formulations preferably comprise polyol ester which has as its reactive components neopentyl polyol and a C12-C20 monocarboxylic acid. Particularly suitable acids to use are C12-C20 branched chain saturated monocarboxylic acids.
The improved rapidly biodegradable grease is provided which performs well at normal temperatures and ambient conditions as well as at more extreme temperatures.
In one embodiment, a grease composition of the invention comprises (a) ester base stock and (b) thickener, wherein the ester base stock comprises a polyol ester of C12-C20 monocarboxylic acid or wherein the ester base stock comprises a blend of two polyol esters where the first of the two polyol esters forms the major component of the blend and is a polyol ester of C12-C20 monocarboxylic acid and the second of the two polyol esters is a minor component of the blend and is a polyol ester of simple C5-C10 carboxylic acid (i.e., C5-C10 monocarboxylic acid), C5-C10 polycarboxylic acids (i.e., C5-C10 dicarboxylic acids) or mixtures thereof.
In another embodiment, the rapidly biodegradable grease composition of the invention comprises (a) ester base stock and (b) thickener, wherein the ester base stock comprises of a polyol ester comprising as its reactive components a neopentyl polyol and a C12-C20 branched chain saturated monocarboxylic acid.
In another embodiment, the readily biodegradable grease composition comprises (a) an ester base stock and (b) thickener wherein the ester base stock comprises a blend of two polyol esters. The first of the two polyol esters forms the major component of the blend and comprises as its reactive components a neopentyl polyol and a C12-C20 monocarboxylic acid, and the second of the two polyol esters forms a minor component of the blend and comprises as its reactive components a neopentyl polyol and a C5-C10 straight chain monocarboxylic acid.
In still another embodiment, the grease composition comprises polyol ester that comprises as its reactive components a neopentyl polyol ester and a C12-C20 branched chain saturated monocarboxylic acid. Alternately, the composition of this embodiment may also comprise a second type of polyol ester wherein the second type of polyol ester comprises as its reactive components a neopentyl polyol and a C5-C10 branched chain saturated monocarboxylic acid.
Other embodiments of the invention include the use of a base stock selected from the group consisting of (1) the trimethylol propane triester of isostearic acid, and (2) a mixture of a major amount of the trimethylol propane triester of isostearic acid and a minor amount of the trimethylol propane triester of pelargonic acid.
Biodegradability is the ability of a chemical compound to be broken down by the biological action of living organisms.
The CEC-L-33-T-82 test for biodegradability was used in the following examples to measure biodegradability. In the Examples, the grease compositions of the invention all had at least 80% biodegradability as determined by this test. A composition with a biodegradability of 80% or more is considered readily biodegradable. The grease compositions of the invention are rapidly biodegradable, and many are readily biodegradable.
Lubricants are agents that reduce friction between moving surfaces. Lubricants can be liquid, solid or of a consistency somewhere between liquid and solid. Greases range from being semi-fluid to being semi-solid.
A lubricating grease may be defined as a semi-solid dispersion of a thickener in a base stock fortified with various additives depending on its intended application.
The base stock of the invention is the synthetic ester or esters described below.
Illustrative aliphatic polyols include neopentyl glycol, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, 2,2,4-trimethyl-1,5-pentanediol, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol, tripentaerythritol or the like. Technical pentaerythritol which contains mono, di-, tri- and higher pentaerythritols in varying proportions can also be used. Neopentyl glycol, trimethylolpropane and trimethylolethane are particularly useful. The polyols are reacted, partially or completely, with an aliphatic monocarboxylic acid or mixture of aliphatic monocarboxylic acids having from 5 to 20 carbon atoms.
The C12-20 aliphatic monocarboxylic acids can be branched or straight-chain and may be saturated or can contain unsaturation. They can be obtained from natural fats or oils or synthetically produced via oxo, Koch or other known reactions. Illustrative aliphatic monocarboxylic acids include lauric acid, myristic acid, palmitic acid, isopalmitic acid, stearic acid, isostearic acid, ricinoleic acid, oleic acid, linoleic acid, and mixtures thereof. Mixed acids derived from coconut oil, lard oil, tall oil, safflower oil, corn oil, tallow, soybean oil, palm oil, castor oil, rapeseed oil, and the like may also be utilized.
Polyol esters obtained from the esterification of trimethylolpropane with C12-20 aliphatic monocarboxylic acids or mixtures thereof, such as trimethylolpropane trioleate and trimethylolpropane triisostearate, are particularly useful. The polyol esters typically have acid values less than 15 and hydroxyl values less than 100. More usually, acid and hydroxyl values of the polyol ester will be less than 8 and less than 25, respectively.
An ester oil is defined herein as a compound having at least one ester functionality and a kinematic viscosity (KIN VIS) of preferably less than about 40 cSt at 100xc2x0 C. Any ester oil may be used which exhibits these characteristics or is preferably at least about 70% biodegradable as measured by the CEC L-33-T-82 method, and most preferably about 80% biodegradable as measured by the CEC L-33-T-82 method.
The oil is particularly useful for use in engines, and more particularly for use in two-cycle engines wherein the gasoline is mixed with the lubricating oil to provide an oil-fuel mixture. The oil according to the present invention burns cleanly with a minimum of soot, ash and carbon formation, so that the engine is free from aggravated carbon deposits on the piston and cylinder heads, and spark plug fouling can be minimized. Further, the oil is preferably biodegradable, and thus is particularly useful in two-cycle outboard engine motors.
The preferred polyester oil which may be used alone or in combination with other heavy ester oils in addition to the light ester oils is produced by the reaction of a triol with an acid and has the following formula: 
wherein R1, R2 and R3 are individually selected from the group consisting of C10 to C30 hydrocarbons which may contain one or more of S, N, and O, and R4 is selected from the group consisting of C1 to C10 hydrocarbons which may contain one or more of S, N and O. More preferably, R1, R2 and R3 are branched or unbranched alkyl radicals having 13 to 20 carbon atoms, and R4 is a branched or unbranched alkyl radical having 1 to 5 carbon atoms.
A more preferred heavyester is the reaction product of a triol with a saturated or unsaturated aliphatic carboxylic acid. Examples of saturated aliphatic carboxylic acids useful for the purposes of this invention include but are not limited to lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid and lignoceric acid. Examples of unsaturated aliphatic carboxylic acids useful for the purposes of this invention include but are not limited to obtusilic acid, caproleic acid, linderic acid, lauroleic acid, tsuzuic acid, physteric acid, myristoleic acid, palmitoleic acid, petroselinic acid, oleic acid, vaccenic acid, gadoleic acid, erucic acid, selacholeic acid, ximenic acid, lumequeic acid, eleostearic acid, parinaric acid, arachidonic acid, clupanodonic acid, and ricinoleic acid. A preferred ester is trimethylolpropane isostearate, having the formula: 
Trimethylolpropane isostearate is sold commercially under the tradename EMERY(copyright) 2951. EMERY(copyright) 2951 exhibits a kin vis of 13.8 cSt at 100xc2x0 C., a kin vis of 102.0 at 40xc2x0 C., a pour point of xe2x88x9218xc2x0 C., a flash point of 286xc2x0 C. and a biodegradability of 93% by CEC L-33-T.82. This oil has superb biodegradability characteristics.
An additional ester which is highly biodegradable and useful for this invention is trimethylolpropane trioleate, sold under the tradename EMERY(copyright) 2964. EMERY(copyright) 2964 exhibits a kin vis of 10.17 cSt at 100xc2x0 C., a kin vis of 48.43 cSt at 40xc2x0 C., a pour point of xe2x88x9240xc2x0 C., a flash point of 312xc2x0 C. and a biodegradability of 99% by CEC L-33-T-82. Trimethylolpropane trioleate may be used as a single heavy ester in combination with a light ester oil, or in combination with one or more heavy ester oils and one or more light ester oils.
The light ester is preferably the reaction product of an alcohol reacted with an acid, and preferably has the following formula: 
wherein R5 and R6 are individually selected from the group consisting of C1 to C20 hydrocarbons which may contain one or more of S, N and O.
More preferably, the light ester is the reaction product of a C5 to C12 branched alcohol reacted with an unbranched C5 to C12 aliphatic carboxylic acid. Examples of aliphatic carboxylic acids (saturated and unsaturated) include but are not limited to pelargonic acid, heptanoic acid, caprylic acid, hexanoic acid, lauric acid, lauroleic acid, capric acid, isovaleric acid, decanoic acid, 4-decehoic acid and 9-deconoic acid. Examples of alcohols (saturated and unsaturated) include but are not limited to isodecyl alcohol, pentyl alcohol, 4-methyl-1-pentanol, 4-penten-2-ol, neopentyl alcohol and 2-isobutyl-5-hexen-6-ol.
The thickening agents of a lubricating grease can be of various types but soaps of lithium, barium, aluminum, calcium and mixtures thereof are the most commonly used systems for bearing greases. They may be used in grease formulations made from ester-based base stocks according to the invention. Other thickening agents that may be used according to the invention include inorganic materials such as silica and clay. These inorganic materials are not biodegradable but they are naturally occurring materials which are generally considered to be environmentally friendly. Preferably, however, soap is used as the thickener in the grease formulations of the invention.
Under some conditions of use, the ester(s) as described above will function satisfactorily as complete lubricants. It is generally preferable, however, for a complete lubricant to contain other materials generally denoted in the art as additives, such as oxidation resistance and thermal stability improvers, corrosion inhibitators, metal deactivators, lubricity additives, viscosity index improvers, pour and/or floc point depressants, detergents, dispersants, antifoaming agents, anti-wear agents, and extreme pressure resistant additives. Many additives are multifunctional. For example, certain additives may impart both anti-wear and extreme pressure resistance properties, or function both as a metal deactivator and a corrosion inhibitor. Cumulatively, all additives preferably do not exceed 8% by weight, or more preferably do not exceed 5% by weight, of the total lubricant formulation.
An effective amount of the foregoing additive types is generally in the range from 0.01% to 5% for the antioxidant component, 0.01% to 5% for the corrosion inhibitor component, from 0.001% to 0.5% for the metal deactivator component, from 0.5% to 5% for the lubricity additives, from 0.01% to 2% for each of the viscosity index improvers and pour and/or floc point depressants, from 0.1% to 5% for each of the detergents and dispersants, from 0.001% to 0.1% for anti-foam agents, and from 0.1%-2% for each of the anti-wear and extreme pressure resistance components. All these percentages are by weight and are based on the total lubricant composition. It is to be understood that more or less than the stated amounts of additives may be more suitable to particular circumstances, and that a single molecular type or a mixture of types may be used for each type of additive component. Also, the examples listed below are intended to be merely illustrative and not limiting.
Examples of suitable oxidation resistance and thermal stability improvers are diphenly-, dinaphtyl-, and phenyl-naphthyl-amines, in which the phenyl and naphthyl groups can be substituted, e.g., N,Nxe2x80x2-diphenyl phenylenediamine, p-octyldiphenylamine, p,p-diocryldiphenylamine, N-phenyl-1-naphthyl amine, N-phenyl-2-naphthyl amine, N-(p-dodecyl)-phenyl-2-naphthyl amine, di-1-naphthylamine, and di-2-naphthylamine; phenothazines such as N-alkylphenothiazines; imino(-bisbenzyl); and hindered phenols such as 6-(t-butyl)phenol, 2,6-di-(t-butyl)phenol, 4-methyl-2,6-di-(t-butyl)phenol, 4,4xe2x80x2-methylenebis(-2,6-di-{t-butyl}phenol), and the like.
Examples of suitable cuprous metal deactivators are imidazole, benzamidazole, 2-mercaptobenzthiazole, 2,5-dimercaptothiadiazole, salicylidine-propylenediamine, pyrazole, benzotriazole, tolutriazole, 2-methylbenzamidazole, 3,5-dimethyl pyrazole, and methylene bis-benzotriazole. Benzotriazole derivatives are preferred. Other examples of more general metal deactivators and/or corrosion inhibitors include organic acids and their esters, metal salts, and anhydrides, e.g., N-oleylsarcosine, sorbitan monooleate, lead naphthenate, dodecanylsuccinic acid and its partial esters and amides, and 4-nonylphenoxy acetic acid; primary., secondary, and tertiary aliphatic and cycloaliphatic amines and amine salts of organic and inorganic acids, e.g., oil-soluble alkylammonium carboxylates; heterocyclic nitrogen containing compounds, e.g., thiadiazoles, substituted imidazolines, and oxazolines; quinolines, quinones, and anthraquinones; propyl gallate; barium dinonyl naphthalene sulfonate; ester and amide derivatives of alkenyl succinic anhydrides or acids, dithiocarbamates, dithiophosphates; amine salts of alkyl acid phosphates and their derivatives.
Examples of suitable lubricity additives include long chain derivatives of fatty acids and natural oils, such as esters, amines, amides, imidazolines, and borates.
Examples of suitable viscosity index improvers include polymethacrylates, copolymers of vinyl pyrrolidone and methacrylates, polybutenes, and styreneacrylate copolymers.
Examples of suitable pour point and/or floc point depressants include polymethacrylates such as methacrylate-ethylene-vinyl acetate terpolymers; alkylated naphthalene derivatives; and products of Friedel-Crafts catalyzed condensation of urea with naphthalene or phenols.
Examples of suitable detergents and/or dispersants include polybutenylsuccinic acid amides; polybutenyl phosphonic acid derivatives; long chain alkyl substituted aromatic sulfonic acids and their salts; and metal salts of alkyl sulfides, of alkyl phenols, and of condensation products of alkyl phenols and aldehydes.
Examples of suitable anti-foam agents include silicone polymers and some acrylates.
Examples of suitable anti-wear and extreme pressure resistance agents include sulfurized fatty acids and fatty acid esters, such as sulfurized octyl tallate; sulfurized terpenes; sulfurized olefins; organopolysulfides; organo phosphorus derivatives including amine phosphates, alkyl acid phosphates, dialkyl phosphates, aminedithiophosphates trialkyl and triaryl phosphorothionates, trialkyl and triaryl phosphines, and dialkylphosphites, e.g., amine salts of phosphoric acid monohexyl ester, amine salts of dinonylnaphthalene sulfonate, triphenyl phosphate, trinaphthyl phosphate, diphenyl cresyl and dicresyl phenyl phosphates, naphthyl diphenyl phosphate, triphenylphosphorothionate; dithiocarbamates, such as an antimony dialkyl dithiocarbamate; chlorinated and/or fluorinated hydrocarbons, and xanthates.
In the prior art pressure additives have often been used in grease formulations. These additives have included: lead compounds, chlorinated hydrocarbons, sulphur, fatty acids and boron derivatives. Corrosion inhibitors such as petroleum sulphonates and aromatic materials in addition to barium and zinc compounds have also been included in product formulations. Solid lubricant additives such as copper, graphite, molybdenum disulphide and PTFE have been added to grease formulations to enhance its performance under arduous conditions. organic polymers along with amines and phenols may also be present to give tackiness and resistance to oxidation. Many of these additives that have been referred to above are not biodegradable. However, when they are tested in relatively minor amounts, the grease formulations of the invention can still have a biodegradability of at least 70%, and preferably 80%.
It is contemplated that suitable inventive greases can be prepared using other known grease additives that have not been specifically mentioned herein.
The two-cycle engine oil of the invention and the grease formulation of the invention are both made, in all embodiments, from an ester base stock wherein the esters of the ester base stock are formed by the reaction of a neopentyl polyol and carboxylic acid. The inventive engine oil and the inventive grease formulation in preferred embodiments both comprise trimethylolpropane triisostearate. Details of preferred embodiments and accompanying examples are set forth below. The two-cycle engine oil is discussed first followed by a discussion of the grease formulation.
A. Ester Base Stocks
Preferred two-cycle engine oil base stocks of the invention are blends consisting essentially of a first polyol ester formed by the reaction of a neopentyl polyol and a C16-C20 branched chain, saturated monocarboxylic acid and a second polyol ester formed by the reaction of a neopentyl polyol and a carboxylic acid selected from the group consisting of (i) at least one C5-C10 straight chain, saturated monocarboxylic acid or (ii) at least one C16-C20 straight or branched chain, unsaturated monocarboxylic acid.
Suitable neopentyl polyols for preparation of the ester blends described above include trimethylolethane, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, neopentylglycol and mixtures of any two or more of such neopentyl polyols. Trimethylolpropane is particularly preferred as the neopentyl polyol reactant in both components of the preferred ester blend described immediately above.
The preferred acids which may be used to form the first polyol ester include the C16-C18 xe2x80x9cisoacidsxe2x80x9d, isostearic acid being particularly preferred. Isostearic acid is a readily available commercial product obtained as a by-product from the manufacture of polymer fatty acids by the polymerization of naturally-occurring, unsaturated C18 fatty acids. It is obtainable under the trademark EMERSOL(copyright) 871 and EMERSOL(copyright) 875 from Henkel Corporation, Emery Group, Cincinnati, Ohio. By way of illustration of the preparation of polymeric fatty acids, reference may be had to U.S. Pat. Nos. 2,793,219 and 2,955,121. Polymeric fatty acids from the polymerization of unsaturated fatty acids are primarily composed of dimer and trimer acids; however, there may also be present in the mixture some higher acids and unreacted monomer. A portion of the C18 monomer acid rearranges during the polymerization to yield a branched-chain C18 monocarboxylic acid product which is then isolated by distillation. Although the exact structure of this C18 branched-chain product has not been fully elucidated, the principal components of the acid are methyl-branched isomers.
Isostearic acid prepared in the manner just described may contain up to 35% by weight saturated, and some unsaturated straight-chain C8-C18 fatty acids. Preferably, these straight chain acids will constitute 25% or less of the isostearic acid reactant. These straight-chain acids are typically present in the isostearic acid as obtained from the polymerization process, however, additional straight-chain acids may be blended with the isostearic acid so long as. the aforementioned limit is not exceeded.
Acid component (i) of the second polyol ester in the preferred ester base stock described immediately above is preferably selected from the group of caproic acid, caprylic acid, pelargonic acid, capric acid and mixtures of two or more of such straight chain, saturated monocarboxylic acids. Particularly preferred as acid component (i) of the second polyol ester are pelargonic acid, or a blend of caprylic (C8) and capric (C10) acids, the latter being commercially available under the trademark EMERY(copyright) 658 from Henkel Corporation, Emery Group, Cincinnati, Ohio. Mixtures of relatively low molecular weight fatty acids (e.g., EMERY(copyright) 1210) may also be used as acid component (i), if desired.
Acid component (ii) of the second polyol ester described is preferably selected from the group of palmitoleic acid, oleic acid and mixtures of such unsaturated monocarboxylic acids. Oleic acid is particularly preferred as acid component (ii).
The ester base stock blends of the present invention are prepared using conventional mixing equipment and techniques. In general, the amount of the first polyol ester in the preferred ester base stock described immediately above should be from about 10% to about 65%, based on the total weight of the ester base stock, and the amount of the second polyol ester present in the blend should be from about 35% to about 90% based on the total weight of the base stock.
Other preferred ester base stocks according to this invention are blends consisting essentially of a first polyol ester formed by the reaction of a neopentyl polyol and a C8-C10 straight chain, saturated monocarboxylic acid and a second, complex polyol ester formed by the reaction of a neopentyl polyol, a C6-C12 dicarboxylic acid and a C5-C10 straight or branched chain saturated monocarboxylic acid.
The preferred neopentylpolyols used in forming the ester base stock of these alternative embodiments of the present invention are essentially the same as those previously described hereinabove. In this embodiment also, TMP is the most preferred neopentylpolyol.
The preferred acid component of the first polyolester of these alternative embodiments includes pelargonic acid or a blend of caprylic and capric acids (e.g., EMERY(copyright) 658), pelargonic acid (e.g., EMERY(copyright) 1202) being particularly preferred.
The complex polyol esters used in preparing the last-mentioned base stocks of the invention are preferably prepared using a blend of caprylic and capric acids (e.g., EMERY(copyright) 658) as the monocarboxylic acid and adipic acid as the dicarboxylic acid components of the complex ester, typically in a weight ratio from about 2.5:1.0 to about 3.0:1.0, caprylic acid-capric acid to adipic acid.
Generally, the amount of the first polyol ester in the ester base stock of these alternative embodiments should be from about 25% to about 85%, based on the total weight of the base stock and the amount of the second polyol ester component should be from about 15% to about 75%, based on the total weight of the base stock.
The above-described ester base stocks may be prepared from relatively pure reagents or from technical grade reagents, e.g., mixed polyols or mixed acids, the reagent mixtures being more economical, because commercially available products may be used, without costly purification as a prerequisite.
The above-described esters are prepared utilizing conventional esterification procedures. Typically, the quantity of acid charged to the reaction mixture initially is sufficient to provide an excess of about 1.1-1.2% of equivalents of acid over the equivalents of alcohol reacted therewith. An equivalent of acid is defined for the purposes of this specification as the amount containing 1 gram equivalent weight of carboxyl groups, whereas an equivalent of alcohol is the amount containing 1 gram equivalent weight of hydroxyl groups. If the reaction mixture contains both monovalent and divalent acids, the excess preferably is made up of the monovalent acid. The esterification reaction is carried out at elevated temperature while removing water. The reaction may be carried out by refluxing the reactants in an azeotropic solvent, such as toluene or xylene, to facilitate removal of water. Esterification catalysts may be used, but are not necessary for the reaction. Upon completion of the reaction, excess acid and any solvent may be conveniently separated from the ester product by vacuum stripping or distillation.
The ester product thus produced may be utilized as such, or it may be alkali refined or otherwise treated. to reduce the acid number, remove catalyst residue, reduce ash content, or other undesired impurities. If the ester product is subject to alkali refining, the resultant product should be washed with water to remove any unreacted excess alkali and the small amount of soap form from the excess fatty acid neutralized by the alkali before using the ester as a base stock and/or lubricant according to this invention.
The ester base stocks of the present invention may optionally include a relatively low molecular weight ester, if desired, as a solvent substitute to enhance fuel/oil miscibility. The solvent substitute-ester may be formed from the reaction of a monohydric alcohol selected from octanol, nonanol, decanol, undecanol, dodecanol, tridecanol and branched chain isomers thereof, and a carboxylic acid selected from the group of valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid and branched chain isomers thereof.
B. Two-cycle Oil Compositions
Various detergent/dispersant additive packages may be combined with the above-described ester base stocks in formulating the two-cycle oil compositions of the invention. Ashless or ash-containing additives may be used for this purpose, ashless additives being preferred.
Suitable ashless additives include polyamide, alkenylsuccinimides, boric acid-modified alkenylsuccinimides, phenolic amines and succinate derivatives or combinations of any two or more of such additives.
Polyamide detergent/dispersant additives, such as the commonly used tetraethylenepentamine isostearate, may be prepared by the reaction of fatty acid and polyalkylene polyamines, as described in U.S. Pat. No. 3,169,980, the entire disclosure of which is incorporated by reference in this specification, as if set forth herein in full. These polyamides may contain measurable amounts of cyclic imidazolines formed by internal condensation of the linear polyamides upon continued heating at elevated temperature. Another useful class of polyamide additives is prepared from polyalkylene polyamines and C19-C25 Koch acids, according to the procedure of R. Hartle et al., JAOCS, 57 (5): 156-59 (1980).
Alkenylsuccinimides are formed by a step-wise procedure in which an olefin, such as polybutene (MW 1200) is reacted with maleic anhydride to yield a polybutenyl succinic anhydride adduct, which is then reacted with an amine, e.g., an alkylamine or a polyamine, to form the desired product.
Phenolic amines are prepared by the well-known Mannich reaction (C. Mannich and W. Krosche., Arch. Pharm., 250: 674 (1912)), involving a polyalkylene-substituted phenol, formaldehyde and a polyalkylene polyamine.
Succinate derivatives are prepared by the reaction of an olefin (e.g., polybutene (MW 1200 700-300)) and maleic anhydride to yield a polybutenyl succinic anhydride adduct, which undergoes further reaction with a polyol, e.g., pentaerythritol, to give the desired product.
Suitable ash-containing detergent/dispersant additives include alkaline earth metal (e.g., magnesium, calcium, barium), sulfonates, phosphonates or phenates or combinations of any two or more of such additives.
The foregoing detergent/dispersant additives may be incorporated in the lubricant compositions described herein in an amount from about 5 to about 20%, and more preferably from about 10% to about 16% based on the total weight of the composition.
Various other additives may be incorporated in the lubricant compositions of the invention, as desired. These include smoke-suppression agents, such as polyisobutylene, extreme pressure additives, such as dialkyldithiophosphoric acid salts or esters, anti-foaming agents, such as silicone oil, pour point depressants, such as polymethacrylate, rust or corrosion prevention agents, such as triazole derivatives, propyl gallate or alkali metal phenolates or sulfonates, oxidation inhibitors, such as substituted diarylamines, phenothiazines, hindered phenols, or the like. Certain of these additives may be multifunctional, such as polymethacrylate, which may serve as an anti-foaming agent, as well as a pour point depressant.
These other additives may be incorporated in the lubricant composition in an amount from about 0.01% to about 15%, and preferably from about 0.01% to about 6%, based on the total weight of the lubricant composition. The amount selected within the specified range should be such as not to adversely effect the desirable performance properties of the lubricant. The effects produced by such additives can be readily determined by routine testing.
The biodegradability of the ester base stocks/lubricant compositions of this invention is xe2x89xa780%, as determined by Co-ordinating European Counsel standard test method L-33-T-82 (Biodegradability of Two-Stroke Cycle Outboard Engine Oils in water), which provides a procedure to evaluate comparatively the biodegradability of two-cycle outboard engine lubricants against the biodegradability of standard calibration materials. In performing this test procedure, test flasks containing a mineral medium, the test oil and a bacterial inoculum (effluent from a municipal sewage plant), together with flasks containing poisoned blanks, are incubated for 0 to 21 days. Flasks containing calibration oils are run in parallel. The tests are carried out in triplicate at 25xc2x11xc2x0 C. and in darkness.
At the end of the incubation period the contents of the flasks are subjected to sonic vibration, acidified and extracted with carbon tetrachloride or 1,1,2-trichlorotrifluoroethane. The extracts are then analyzed by infra-red spectroscopy, measuring the maximum adsorption of the CH3-CH2-bond at 2930 cmxe2x88x921.
Biodegradability is expressed in % as the difference in residual oil contents between the poisoned flasks and the respective test flasks.
Details of reference and standardization lubricants are. to be found in the CEC Handbook of Reference/Standardization Oils for Engine/Rig Tests. The biodegradability of the ester base stocks of the invention is preferably xe2x89xa790%, as determined by the same CEC standard test method mentioned above. A biodegradability value below 80% for the ester base stocks, according to the aforementioned CEC. standard test method, is not considered to be readily biodegradable.
The ester base stocks/lubricant compositions of the invention have a flash point of xe2x89xa7175xc2x0 C., and preferably xe2x89xa7250xc2x0 C. Such flash point properties are a decided improvement over prior art ester base stocks containing miscibility enhancing solvents, such as Stoddard solvent, which has a flashpoint of about 40xc2x0 C.
The ester base stocks/lubricant compositions of the invention have desirably low viscosities of less than 15 cSt at 100xc2x0 C. Preferably, the viscosity at 100xc2x0 C. is in the range of 7-9 cSt. At viscosities much above 15 cSt at 100xc2x0 C., the corresponding viscosity at xe2x88x9225xc2x0 C. is such that the miscibility of the ester base stock/lubricant in gasoline is reduced.
The miscibility of the two-cycle engine oil composition of the invention with gasoline, in a fuel/oil ratio of 16:1 to 100:1 is generally xe2x89xa6110% relative to a reference oil, as determined by ASTM-4682 using Citgo-93738 as the reference oil for category 3, as outlined in SAE J1536.
The two-cycle engine oil compositions of the present invention are particularly suited, when mixed with an appropriate fuel, for operating outboard motors, snow mobiles, mopeds, lawnmowers, chain saws, string trimmers and the like.